Living near heavy traffic increases risk of dementia, scientists say
Roughly one in 10 cases of Alzheimer’s in urban areas could be associated with living amid heavy traffic, a study estimated
People living near a busy road have an increased risk of dementia, according to research that adds to concerns about the impact of air pollution on human health.
Roughly one in 10 cases of Alzheimer’s in urban areas could be associated with living amid heavy traffic, the study estimated – although the research stopped short of showing that exposure to exhaust fumes causes neurodegeneration.
Hong Chen, the scientist who led the work at Public Health Ontario, said: “Increasing population growth and urbanisation has placed many people close to heavy traffic, and with widespread exposure to traffic and growing rates of dementia, even a modest effect from near-road exposure could pose a large public health burden.”
Previously, scientists have linked air pollution and traffic noise to reduced density of white matter (the brain’s connective tissue) and lower cognition. A recent study suggested that magnetic nano-particles from air pollution can make their way into brain tissue.
The latest study, published in The Lancet, found those who live closest to major traffic arteries were up to 12 per cent more likely to be diagnosed with dementia – a small but significant increase.
The study, which tracked roughly 6.6 million people for more than a decade, could not determine whether pollution is directly harmful to the brain.
The increased dementia risk could also be a knock-on effect of respiratory and cardiac problems caused by traffic fumes or due to other unhealthy lifestyle factors associated with living in built-up urban environments.
However, Ray Copes, chief of environmental and occupational health at Public Health Ontario, and a co-author of The Lancet paper, said that those living in cities should consider walking along side streets, jogging in parks and planning cycle routes along quieter roads where possible.
“Air pollutants can get into the blood stream and lead to inflammation, which is linked with cardiovascular disease and possibly other conditions such as diabetes. This study suggests air pollutants that can get into the brain via the blood stream can lead to neurological problems,” Copes said.
However, others cautioned that those living close to main roads should not be unduly alarmed by the findings.
The scientists found no link between living near a road and Parkinson’s disease or multiple sclerosis, but dementia was slightly more common in people living close to busy roads and the risk dropped off gradually in less built-up areas.
Those living within 50 metres of a busy road had a 7 per cent higher risk in developing dementia, the risk was 4 per cent higher risk at 50-100 metres, 2 per cent higher risk at 101-200 metres and there was no increase in risk in those living more than 200 metres away.
Those who lived in a major city, within 50 metres of a major road and who did not move house for the duration of the study had the highest risk at 12 per cent, the study found.